1. Field of the Invention
The present invention relates to an angular speed detecting device that detects the rotation speed of a rotating object.
2. Description of the Related Art
A magnetic sensor unit that is composed of a pair of magnetic sensing elements and a magnetic field setting member is well-known for a device to detect the rotation angle of a rotating object, as disclosed in JP-A-2002-340511. In such a device, a pair of sensor elements provides signals Va and Vb, as shown in FIG. 16. Then, a saw-tooth-wave curve of trigonometric values θ′ that correspond to the arctangent of the signals Va and Vb, is provided as shown in FIG. 17. Then, plural rotation angle ranges of the rotating object between 0 degree and 360 degrees can be known from combinations of the positive and negative signs of the output signals Va and Vb, as shown in FIG. 20. Therefore, the rotation angle of the rotating object in terms of 360 degrees can be known from the output angle θ, as shown in FIG. 18, so that the angular speed of the rotating object can be obtained by differentiating the output angle θ in theory. However, when one intends to obtain the angular speed of the rotating object from the rotation angle around 360 degrees from the output angle θ, he will have a difficulty because the output angle θ before or after 360 degrees changes too sharply to differentiate it, as shown in FIG. 19.